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Re: Software Recommendations (seismic)

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We have been using DesconBrace and DesconWin for about three years now and it is a pretty good program for designing steel moment and brace connection.  Like any other program you need to be knowledgeable with their default parameters and carefully review the results.

As for R values, be very careful as the old adage of R >3 and R<3 no longer applies,   There are now several cases where seismic detailing is required for R values less than 3 and IBC Section 2205.2.2 requires seismic detailing for all steel structures in Seismic Categories D, E, and F regardless of R value.   For piperacks you need to look at ASCE 7-05 Table15.4-1 and in particular footnotes b, c, and d.  The R value can range from 1 to 8.  Since your piperack is only 14 feet tall you may want to go with an R of 3.5 for ordinary moment frames.  If you are not in Seismic Categories D, E, or F then you may want to go with an R value of 1.0 and forget the seismic detailing all together.  R values of 4.5 and 8 for Intermediate and Special moment frames are available however the design and detailing requirements can be quite onerous.  For piperacks, the R value is more of an economic issue of how much steel (plus anchor bolt and foundation sizing) do you want to save versus the engineering time you might want to put into your design.

Thomas Hunt, S.E.

"Teo, KP" <KP_Teo(--nospam--at)>
07/18/2008 04:33 AM
Please respond to seaint
"ron jackson" <rjackson(--nospam--at)>
Software Recommendations (seismic)

Does anybody have a good software recommendation to perform seismic design calculations per AISC 341-05 - Seismic Design Manual?
We have just adpoted IBC2006/ASCE7-05 which references to this manual when R>3 (in most cases) and for most non-building structures. Since different components and connections of the SLRS(Seismic Load resisting System) requires different factors to be applied (ie.Omega factor, expected yield), compactness check (Compact & Seismically Compact)...etc, it can get relatively complex for both designer and checker. Adding to the complexity is this book only uses LRFD, which is very different for someone that is already used to the ASD equations.
Therefore i am looking for a user friendly, well organized and accurate software that will perform this task. I know DESCON (Design Connections) now is an add-on to StaadPro. Have anyone use it before and does it do the AISC 341-05 check? I have used the DOS version in the past and it is a good software in my opinion.
As a side question, what kind of system (R Value) would you consider a piperack (non-building) with concrete piers constructed to approximately 14 ft height, and steel moment frame modules (constructed off-site and lifted in place) sitting on top of the piers with a fixed-base connection?
Thank you in advance for your kind comments.
KP Teo

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